1. Field of the Invention
The present invention relates to an ink jet recording head using a piezoelectric vibrator as a driving source.
2. Related Art
There has been known a conventional ink jet recording head for sucking ink and ejecting ink droplets by expanding or contracting a pressure generating chamber partly constituted by an deformable plate which communicates with a nozzle aperture by a piezoelectric vibrator. The conventional ink jet recording head suffers from a problem that the quantity of ink in a ejected ink droplet is greatly influenced by the change of the viscosity due to the change of temperature because an ink droplet is ejected by pressure. That is, the quantity of ink increases as temperature rises as shown in FIG. 16 and the quality of printing is varied.
In view of the afore-mentioned problem, there has been proposed a driving technique for fixing the quantity of ink by changing the rate of the contraction of a pressure generating chamber according to ambient temperature and adjusting the magnitude of a signal applied to a piezoelectric vibrator and variable acceleration when an ink droplet is ejected to temperature.
Hereby, the quantity of ink in an ink droplet can be held so that it is fixed independent of temperature by changing the level of a signal applied to a head according to temperature. However, as the speed and quantity of the contraction of a pressure generating chamber come to vary, the speed and stability of the ejecting of ink droplets are readily deteriorated particularly in printing requiring the formation of a minute dot such as graphic data. Therefore, there still arises a problem that the speed of the ejecting of ink droplets is deteriorated and unstable and the quality and the stability of printing are deteriorated.
To solve such deficiency, there has been proposed, as disclosed in Unexamined Japanese Patent Application No. Hei. 9-309206, another ink jet recording apparatus which is provided with an ink jet recording head made of nozzle apertures, a pressure generating chamber communicating with a common ink chamber via an ink supply port and a piezoelectric vibrator for expanding or contracting the pressure generating chamber and signal generating means for generating a first signal for expanding the pressure generating chamber depending upon the change of potential from intermediate potential at which voltage from reference potential varies depending upon temperature to the reference potential, a second signal generated for raising the potential from the reference potential to the maximum voltage for contracting the pressure generating chamber to eject an ink droplet and a third signal for restoring the contracted pressure generating chamber after an ink droplet is ejected for holding the weight of an ink droplet and the speed of ejection fixed independent of temperature by setting the intermediate potential to a higher value when temperature rises.
However, such proposed apparatus still causes another problem that it is difficult to control the position of a meniscus based upon temperature, that is, the viscosity of ink.
Therefore, there is a problem that a range in which the quantity of ink in an ink droplet which can eject in stable is adjusted is small and, particularly, it is difficult to form a small dot suitable for graphic printing independent of temperature.